notification_center.py

notification_center.py

from objc_util import *
import console
from functools import partial
NSNotificationCenter=ObjCClass('NSNotificationCenter')



#logging.basicConfig(filename='log.txt',format='%(levelname)s:%(message)s', level=logging.DEBUG)

class NotificationObserver(object):
	''' Create a Notification oobserver for notification named name, and callback the callable callback.
	if name is none, respond to all notifications, though exclude notifications starting with excludes
	
	callback should be of form:def cb(name,obj, userInfo)
	name can be a specific notification name, or None. None captures all notifications unless filtered by excludes/namefilter
	excludes can be a tuple or list of strings to exclude using startswith
	namefilter is a string, or None, and looks for names startung with some prefix
	'''
	def __init__(self, callback=None, name=None, excludes=('UI','NS','_UI'),namefilter=None)	:
		#self.captured=[]
		self.captured={}
		self.center=NSNotificationCenter.defaultCenter()
		self.name=name

		self.namefilter=namefilter
		if not name:
			self.excludes=excludes
		else:
			self.excludes=[]
		if callable(callback):
			self.callback=callback
		else:
			self.callback=None
		self._observer=None
		self._blk=None
		
	def _block(self,_cmd,notification):
		try:
			name=str(ObjCInstance(notification).name())
			if self.excludes and name.startswith(self.excludes):
				return
			if self.namefilter and not name.startswith(self.namefilter):
				return
			obj=str(ObjCInstance(notification).object())
			userInfo=str(ObjCInstance(notification).userInfo())
			if self.callback:p and callable(self.callback):
				self.callback(name, obj, userInfo)
		except Exception as e:
			raise 
	def start(self):	
		if self._observer:
			raise Exception('observer already started')
		self._blk=ObjCBlock(self._block,
												restype=None,
												argtypes=[c_void_p,c_void_p])
		self._observer = \
			self.center.addObserverForName_object_queue_usingBlock_(self.name,None,None,self._blk)
		#retain_global(self)

	def stop(self):	
		import objc_util
		if self._observer:
			self.center.removeObserver_(self._observer)
			self._observer=None
		release_global(self)
	def reset(self):
		self.stop()
class Canary:
	def __init__(self, g):
		@on_main_thread
		def die():
			print('canary died')
			g.center.removeObserver_(g._observer)
			g._blk=None
			g.callback=None
		import weakref
		self._ref=weakref.finalize(self,die)
if __name__=='__main__':
	def cb(name,obj,userInfo):
		print( 'notification',name,'\nobject: ',obj,'\nuserinfo: ',userInfo)
		#g.captured=True
	g=NotificationObserver(callback=cb,name='UIApplicationDidEnterBackgroundNotification')
	g.start()
	print('started watching for bg notifications')
	'''there may be a better way to do this, but i couldnt get it to work, because there are some stubborn references to the notificationObserver that prevent it from actually getting gc'd. so, i create a "canary" that will be killed first when globals get cleared.  the canary weakref finalize takes care of stopping the observer, so we are not getting duplicate notifications, and trying to clear some references that might keep it from getting gc'd later'''
	canary=Canary(g)